#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int main()
{
	int i, n, sum,t;
	sum = 0;
	t = 1;
	printf("Please input value of n:");
	scanf("%d", &n);
	for (i = 1; i <= n*2-1; i +=2)
	{
		sum = sum + t;
		t = -t * (i + 2) * (i + 1);

	}
	printf("sum=%d\n", sum);
	return 0;
}